Performer's sample disc boomed back briefly (4)
I believe the answer is:
demo
'performer's sample' is the definition.
'demo' can be an answer for 'sample' (I've seen this in another clue). I'm not sure about the 'performer's' bit.
'disc boomed back briefly' is the wordplay.
I cannot quite see how this works, but
'disc' could be 'o' (disc-shaped letter) and 'o' is found within the answer.
The remaining letters 'dem' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for demo that I've seen before include "exhibit" , "March (abbr)" , "Brass instrument valve" , "Public protest meeting" , "In brief, a public event as of protest under dome" .)